Jun Fan and Jeet Kune Do are not exactly the same . Jun Fan is more of a basic course emphasizing Lee's modified Wing Chun etc. say pre 1967. JKD is more or less the "graduate work"... say from the late 60's onward..it is actually more of a personal research and development...following a" research model" established by Lee. Lee's personal JKD passed on when he did.
Once again this is just a rough description- off the top of my head so to speak. Bruce's JKD evolved from the Jun Fan Arts. Trying to explain all this is kind of like trying to wrap a pound of water.
There used to be a sign in Danny and Richards old school it said, "What is Jeet Kune Do ?" The sign was above a large mirror.
As to Norris he, Joe Lewis and others had a student teacher relationship with Bruce for awhile. I forgot to mention Dan Lee and Richard Bustillo as orginal JKD students. Dan Lee teaches tai chi and JKD in California. Richard teaches Kali/escrima and his JKD at his own academy. There others like Kareem Abdul Jabar who studied with Bruce for a while.
Bruce lee learnt most of his wing chun under wong shun leung. He only learnt a small amount of wing chun and i think this is why he created Jeet kune do. he felt wing chun didn't have all the anwser BUT he had not studied it in great lenght. Its like a jig saw puzzel and he used other styles to finish off the puzzel. As for difference in the 2 concepts i'll leave you with the words of Bruce Lee: "we are all on different mountines, but when we look up, we see the same sky".